The Super Bowl and other major sporting events

Early in the reading of "Everything New is Old Again" the major sporting event, the Super Bowl is mentioned and how different television companies have the rights to various sporting events. Why does CBS have the Super Bowl? What doe ABC have the NBA Finals? Why does NBC get the Olympics? Watching these major sporting events throughout my life, I have never asked the question until now as to how does each television company win the rights to these major events and is there rules as to how many you can broadcast due to fairness? I'm not a die-hard NFL fan but I will watch the Vikings. It never occurred to me that only AFC games are on NBC, only NFC games are on CBS, and Monday Night Football is always on ABC. These companies pay millions and millions of dollars to be able to broadcast these events but it does make sense, when they broadcast the programming, they get to choose whichever advertising they want to provide to the viewers. While watching the Super Bowl this year, it was almost overwhelming with the amount of CBS television shows that were constantly being advertised during the commercials. The same goes for the Olympics and NBC shows but that lasts for a few weeks. I wonder if there is a limit as to how many major events one can broadcast and that ties into major award shows as well such as the Oscars and the Grammys. Are there certain regulations they have to follow when airing major events? I think that it would only make sense for the sense of business to spread out these events among the major networks.

DQ: Should a television network be able to dominate all other channels with the acquisition of major events?